Field of the Invention
The present invention relates to a technical improvement of a belt-type continuously variable transmission for a working machine.
Description of the Related Art
A belt-type continuously variable transmission for a working machine is a transmission capable of continuously changing a speed reduction ratio of a driven pulley to a drive pulley. In order to enhance the working efficiency of a working machine and the degree of freedom of work, it is preferable that a worker can optionally regulate the working speed of the working unit, and the traveling speed of the traveling unit, in accordance with a working situation.
As a working machine like this, an auger snowplow is cited, for example. A general auger snowplow can scrape up snow by the auger at a front part while traveling forward by a power source, and blow the snow which is scraped up to a distance via a chute by a blower. A load that is applied to the auger and the blower, that is, the load on the snow removal working unit successively changes due to various factors such as the density of snow, a snow removal height, and a snow throwing distance. In this relation, the art in which a belt-type continuously variable transmission is interposed in a working power transmission system from a drive source to a snow removal working unit is known from Japanese Utility Model Publication No. 05-040096, for example.
The belt-type continuously variable transmission known from Japanese Utility Model Publication No. 05-040096 is composed of a drive pulley that is provided at an output shaft of an engine, a driven pulley that is provided at a drive shaft of an auger and a blower, a V-belt that is laid between the drive pulley and the driven pulley, and a tension pulley that is located in the middle of the V-belt. The driven pulley is composed of a fixed sheave provided at the drive shaft, a movable sheave displaceable in an axial direction with respect to the fixed sheave, and a spring that urges the movable sheave to the fixed sheave. The tension pulley is driven by a hydraulic cylinder to advance and retreat with respect to the V-belt.
A worker optionally operates an operation unit in accordance with the quality of snow to be removed. A control device extends and contracts the piston of the hydraulic cylinder by performing drive control of a hydraulic pump in accordance with the operation signal of the operation unit. When the piston extends, and thereby the tension pulley presses the V-belt, the tension of the V-belt increases. In accordance with increase in tension, the movable sheave moves away in the axially longitudinal direction with respect to the fixed sheave. When the piston contracts, and thereby the pressing force to the V-belt by the tension pulley reduces, the tension of the V-belt decreases. In accordance with decrease in the tension, the movable sheave moves closer to the fixed sheave. In this manner, in accordance with the displacement amount of the movable sheave to the fixed sheave, an effective diameter of the driven pulley changes. As a result, the speed reduction ratio of the driven pulley to the drive pulley can be continuously changed.
The driven pulley of an ordinary belt-type continuously variable transmission is provided with a well-known torque cam mechanism. The torque cam mechanism converts a part of torque that is transmitted to the movable sheave from the V-belt into a thrust, and is known from Japanese Patent Laid-Open No. 05-060192, for example. It is preferable to also provide the torque cam mechanism in the belt-type continuously variable transmission which is known from Japanese Utility Model Publication No. 05-040096. A belt-type continuously variable transmission can smoothly perform a displacement operation of the movable sheave by including the torque cam mechanism.
However, in order to enhance snow removing workability in the case in which the snow throwing place where snow is thrown from an auger snowplow is narrow, and in the case in which snow removing work is performed in a densely built-up residential area, there is yet room for further improvement. That is, the load on the snow removal working unit can instantly increase and decrease due to various abrupt change factors such as the density of snow to be removed, and the snow removing height. When the load is abruptly decreased, a movable sheave temporarily moves away from a fixed sheave by the action of a torque cam mechanism accompanying the abrupt decreases. Consequently, the rotational speed of a blower can temporarily become a high speed. When the blower has a high speed, the snow throwing distance from the chute becomes long. Even in the case like this, in the densely built-up residential area, a careful operation is required so that thrown snow does not enter the grounds of adjacent houses.
In relation to this, the worker frequently needs to adjust the snow throwing direction and the snow throwing angle of the chute, and the operation is troublesome. In addition, the work is adjusting the snow throwing direction and the snow throwing angle frequently while moving the auger type snowplow forward, and therefore, a burden on the worker is large. In this way, in order to enhance the snow removing workability of the auger snowplow, there is yet room for further improvement. The same also applies to various working machines.
The present invention has an object to provide an art that can enhance workability of a working machine including a belt-type continuously variable transmission.